Brandon Sanderson
Chapter Thirty-Eight - Part Three
My one disappointment with this chapter is that I had to end up making it look like I was breaking my own rules. The Allomancy-Feruchemy-Hemalurgy triad is one of the most complex magic systems I've ever devised. The interplay between the three systems, mixed into the mythology of the setting (which involves the mists at a foundational level) makes for some very complicated rules. I try to explain them as simply as possible–simple, basic rules are necessary for most sequences to work.
Yet, the depth of complexity leads to some things that are confusing at first glance. I wasn't planning on having Vin draw upon the mists in this book–I was going to save it for later–but the initial version of this chapter (which had Vin simply grabbing the bracelets off the Lord Ruler’s arms with her hands) lacked the proper drama or impact. So, I moved up my timetable, and gave her access to some abilities she wasn't going to get until the next book.
A lot of the "Rules" of Allomancy are, in my mind, like our basic rules of physicist. They make simple sense, and can be explained easily. However, they only apply when generalities–or large-scale events–are explained. When you get down to the really advanced physics, traditional Newtonian Laws start to break apart.
The same is true for Allomancy. The vast majority of Allomancers aren't powerful enough to look beyond the basics. For them, simple rules like "You can't Push on metals inside of someone's body" apply. It's much easier to tell someone that, as opposed to "People's bodies interfere with Allomancy, making it much harder to affect metals inside of them–so hard, in fact, that only some people you'll never meet can Push on metals inside of people's bodies."
It is a matter of degree of power. Vin, for reasons I'll explain eventually, has access to far more Allomantic power than regular people. The Lord Ruler is the same way, though for different reasons. And so, he can affect metals that are blocked by blood. Vin has to draw upon another, external source of power in order to produce the same effect, but it is possible for her.
Narratively, I worry that this looks too much like I'm breaking my own rules. However, I had to balance drama with effect in this chapter, and eventually decided that I could make it work. I've established throughout the book that there are flaws in the commonly-perceived laws of Allomancy. There are metals nobody knows about. You can pierce copperclouds. In fact, one of the unwritten laws of Allomancy is that it isn't understood as well as everyone seems to think.